A systematic screening of the depigmenting capacity of a variety of phenolics and catecholics, and their congeners is under study. Laboratory animals being used are black guinea pigs and black mice. The object is to provide a model in vivo and in vitro system to demonstrate the depigmenting capacity of known and suspect depigmenting chemicals and to study the pathomechanisms of chemically induced depigmentation found in occupational and industrial diseases. This includes histological, histochemical, and autoradiographic examination of normal, irritated and depigmented animal skin with light and electron microscopy. In addition, we will try to develop a chemical and quantitative technique to screen chemical agents which cause skin depigmentation.